M51
The Chandra X-ray telescope captured this stunning view of Messier 51.
Credit: X-ray: NASA/CXC/Wesleyan Univ./R.Kilgard, et al; Optical: NASA/STScI
Credit: Lowell Observatory
Whirlpool Galaxy: Exploding With Supernovas
by Elizabeth Howell, SPACE.com | April 15, 2014 01:29am ET
The Whirlpool Galaxy is a spiral galaxy that is relatively close to Earth — about 30 million light-years away. It is visible in the northern constellation Canes Venatici, just southeast of the Big Dipper.
More properly known as M51 or NGC 5194, the galaxy is noted as "one of the brightest and most picturesque" ones that Earthlings can see, according to NASA. The Space Telescope Science Institute (STScI) calls it one of "astronomy's galactic darlings."
Among astrophysicists, one of the Whirlpool's highlights is the abundance of supernovas (star explosions) that have been recorded there in recent years. It also is noted for its closeness to companion galaxy NGC 5195, which may be affecting the structure of the Whirlpool itself.
'Spiral nebula'
M51 was first catalogued by Charles Messier in 1773 while the astronomer was plotting objects in the sky that could confuse comet-hunters. "M51" is a reference to "Messier 51," one of about 110 entries now plotted in his Catalogue of Nebulas and Star Clusters. (The companion NGC 5195 was discovered in 1781 by Pierre Méchain, who the University of Manitoba describes as a close friend to Messier.)
It would take about 70 years to learn more about the fuzzy object's structure, however. It was first discerned by William Parsons, 3rd earl of Rosse, using a 72-inch reflector telescope in 1845. "His drawing of the spiral galaxy M51 is a classic work of mid-19th-century astronomy," said Encyclopedia Britannica of Parsons' observations.
Parsons' discovery was the first so-called "spiral nebula" ever discovered, and in the five years following he found 14 more of these objects, according to the STScI. It was unclear for decades if these objects were a part of the Milky Way Galaxy or things that were independent of that.
It wasn't until Edwin Hubble used Cepheid variable stars to chart cosmic distances in M31 (the Andromeda Galaxy) in the 1920s that astronomers understood they were actually distant galaxies.
Whirpool galaxy before and after supernova
The Whirlpool galaxy (M51) before (left) and after (right) the eruption of supernova SN 2011dh in May 2011. The image on the left was taken in 2009, and on the right July 8th, 2011.
Credit: Conrad Jung
Supernova bonanza
There's been a veritable cornucopia of supernovas in the Whirlpool in recent years. Skywatchers recorded supernovas in 1994, 2005 and 2011.
"Three supernovas in 17 years is a lot for single galaxy, and reasons for the supernova surge in M51 are being debated," noted the NASA website Astronomy Picture of the Day in 2011, without elaborating on the possible explanations.
The latest supernova, called SN 2011dh, was at its brightest in June 2011 before slipping back into obscurity. After the event, astronomers scoured older pictures to see if they could find the source of the explosion. They narrowed their search to a yellow supergiant star (visible in Hubble Space Telescope pictures) that was there before the explosion, and appears to be missing afterwards.
While most yellow supergiants aren't expected to go supernova when they finish out their lives, the team said it's possible that the star was actually a binary star. The other star would have been a bluer, hotter star that was close enough to pull some of the yellow supergiant's mass away. Given enough time, this would have destabilized the star and caused the explosion, astronomers said.
The blue star wasn't spotted in Hubble photos, but astronomers added that it is likely best visible in ultraviolet light — a band of light that Hubble does not look at.
"The present results reveal the necessity and importance of further studyingthe evolution and explosion of binary stars," said Melina Bersten of the Kavli Institute for the Physics and Mathematics of the Universe in Japan, who led the team, in a statement. "I look forward to the observation that will confirm our prediction."
Close encounter of the galactic kind
The Whirlpool's arms are one of the more prominent observed in spiral galaxies, STScI noted. The group said this could be because of what they termed a "close encounter" with its companion galaxy, NGC 5195.
"As NGC 5195 drifts by, its gravitational muscle pumps up waves within the Whirlpool's pancake-shaped disk. The waves are like ripples in a pond generated when a rock is thrown in the water," STScI stated.
"When the waves pass through orbiting gas clouds within the disk, they squeeze the gaseous material along each arm's inner edge. The dark dusty material looks like gathering storm clouds. These dense clouds collapse, creating a wake of star birth."
Over time, the biggest stars would then radiate away the surrounding gas, leaving behind blue star clusters that are easily visible in the Whirlpool's arms, STScI added. More generally, the fact that the galaxy is so close by allows astronomers to look at its structure and way it forms stars, with the aim of extrapolating that understanding to other galaxies.
Blood Moon
Skywatching 2014
A meteorite streaks across the Australian night sky, in front of the Milky Way.
Image credit: Alex Cherney/terrastro.com
Video credit: Alex Cherney/terrastro.com
By Joe Rao, Space.com Skywatching Columnist | March 31, 2014 05:49pm ET
From eclipses and planets to meteor showers galore, the northern spring season of 2014 will bring a number of eye-catching celestial sights for stargazers on Earth.
Weather permitting, some of the best spring night sky events could be readily visible without the aid of binoculars or a telescope, even from brightly-lit cities. But you'll need to know when and where to look to make the most of the season.
I've always felt that many astronomers started their careers as perceptive children who responded to the thrill of witnessing a noteworthy astronomical event. So whether you want to impress a youngster, or you're simply hoping to witness a head-turning astronomical event for yourself, it always helps to be ready in advance by marking your calendar and highlighting a number of these special dates:
April 14 and15: Mars' closest approach in 2014 and a total eclipse of the moon!
During the overnight hours of April 14 and 15, it will be a night for viewing first Mars and later the full moon.
First, Mars will come to within 57.4 million miles (92.4 million kilometers) of our planet, making its closest approach to us since Jan. 3, 2008. All through the night, Mars will resemble a dazzling star shining with a steady fiery-colored tint making it a formidable sight; its brightness will match Sirius, the brightest of all the stars.
As a bonus, later that very same night (actually during the early hours of April 15) North America will have a ringside seat to see a total lunar eclipse when the Full Moon becomes transformed into a mottled reddish ball for 78 minutes as it becomes completely immersed in the shadow of the Earth.
This total lunar eclipse will be the first one widely visible from North America in nearly 3.5 years. The Americas will have the best view of this eclipse, although over the Canadian Maritimes, moonset will intervene near the end of totality. Of special interest is the fact that the moon will appear quite near to the bright star Spica, in the constellation Virgo, during the eclipse. They actually will be in conjunction a couple of hours prior to the onset of totality, but they're still relatively near to each other when the eclipse gets underway.
The year 2014 is packed with amazing night sky events. See the year's most exciting celestial events to mark on your calendar in this Space.com infographic.
Credit: Jennifer Lawinski space.com
Rather favorable circumstances are expected for this year’s Lyrid meteor shower, predicted to be at maximum this morning. The radiant, located near the brilliant bluish-white star Vega, rises in the northeast about the time evening twilight ends, and viewing will improve until light from the last-quarter moon begins to interfere just after 2 a.m. your local time.
Under the best conditions, 10 to 15 members of this shower can be seen in an hour by a single observer. The Lyrids remain about a quarter of their peak number for about two days. These bright meteors are associated with Thatcher’s Comet of 1861.
April 28 and 29: A Ring Eclipse that nobody will see?
It is quite possible that only penguins will witness the annular solar eclipse, also known as a "ring of fire" solar eclipse. That's because it will occur within the uninhabited region of Wilkes Land in Antarctica.
Those living in southernmost parts of Indonesia as well as Australia (where it will be autumn) will at least get a view of a partial eclipse of the sun. Because the axis of the moon's antumbral shadow misses the Earth and only its edge grazes Antarctica, it makes an accurate prediction of the duration of annularity all but impossible.
May 6: The Eta Aquarid meteor shower
The annual Eta Aquarid meteor shower — "shooting stars" spawned by the famed Halley's Comet — is scheduled to reach maximum early this morning. It's usually the year's richest meteor display for Southern Hemisphere observers, but north of the equator the Eta Aquarid shower is one of the more difficult annual displays to observe.
From mid-northern latitudes, the radiant (from where the meteors appear to emanate) rises about 1:30 a.m. local daylight time, scarcely two hours before morning twilight begins to interfere. At peak activity, about a dozen shower members can be seen per hour by a single observer with good sky conditions from latitude 26 degrees North, but practically zero north of latitude 40 degrees. The shower remains active at roughly one-half peak strength for a couple of days before and after the maximum. Conditions this year are excellent; the moon is absent from the predawn sky for more than a week around maximum.
May 10: Saturn at opposition
The ringed planet Saturn reaches opposition; it rises in the east-southeast at dusk, is due south in the middle of the night and sets in the west-southwest at dawn. Once it gains enough altitude, it appears similarly as bright as the zero-magnitude stars Arcturus and Vega.
Saturn's famous rings appear much more impressive than in recent years, since they are now tipped by 21.5 degrees from edge on.
May 24: Possible outburst of bright meteors
Perhaps the most dramatic sky event in 2014 could come at the start of the Memorial Day weekend. In the predawn hours of Saturday, May 24, our planet is expected to sweep through a great number of dusty trails left behind in space by the small comet P/209 LINEAR.
This unusual cosmic interaction might possibly result in an amazing, albeit brief display of meteors — popularly known as "shooting stars" — perhaps numbering in the many dozens …or even hundreds per hour. Nobody knows exactly how many meteors will be seen, but several meteor scientists believe that because the particles will be unusually large, the meteors will be outstandingly bright.
May 25: Mercury attains its greatest elongation
The planet Mercury will reach its greatest elongation, or greatest angular distance, east of the sun on this night. This is Mercury's best evening apparition of the year; it sets about 100 minutes after sunset. An hour after sunset, look low above the west-northwest horizon; the speedy planet should be easily visible as a yellowish "star."
Mercury will appear somewhat brighter up to two weeks before this date, and noticeably dimmer for about a week afterwards.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. space.com
Pink Planet GJ 504b
Pink Alien Planet Is Smallest Photographed Around Sun-Like Star
by Megan Gannon, News Editor | August 06, 2013 11:32am ET
www.space.com
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Glowing a dark magenta, the newly discovered exoplanet GJ 504b weighs in with about four times Jupiter's mass, making it the lowest-mass planet ever directly imaged around a star like the sun. This image is an artist's representation of the alien world.
Credit: NASA's Goddard Space Flight Center/S. Wiessinger
This composite combines Subaru images of GJ 504 using two near-infrared wavelengths (shown in orange and blue). Once processed to remove scattered starlight, the images reveal the orbiting planet, GJ 504 b.
Credit: NASA’s Goddard Space Flight Center/NOA
by Megan Gannon, News Editor | August 06, 2013 11:32am ET
www.space.com
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Credit: NASA's Goddard Space Flight Center/S. Wiessinger
Astronomers have snapped a photo of a pink alien world that's the smallest yet exoplanet found around a star like our sun.
The alien planet GJ 504b is a colder and bluer world than astronomers had anticipated and it likely has a dark magenta hue, infrared data from the Subaru Telescope in Hawaii revealed.
"If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color reminiscent of a dark cherry blossom, a dull magenta," study researcher Michael McElwain, of NASA's Goddard Space Flight Center in Greenbelt, Md., said in a statement from the space agency.
Credit: NASA’s Goddard Space Flight Center/NOA
"Our near-infrared camera reveals that its color is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds," McElwain added.
The exoplanet orbits the bright star GJ 504, which is 57 light-years from Earth, slightly hotter than the sun and faintly visible to the naked eye in the constellation Virgo. The star system is relatively young at roughly 160 million years old. (For comparison, Earth's system is 4.5 billion years old).
Though it is the smallest alien world caught on camera around a sun-like star, the gas planet around GJ 504 is still huge — about four times the size of Jupiter. It lies nearly 44 Earth-sun distances from its central star, far beyond the system's habitable zone, and it has an effective temperature of about 460 degrees Fahrenheit (237 Celsius), according to the researchers' estimates.
The exoplanet's features challenge the core-accretion model of planet formation, they study's researchers say. Under this widely accepted theory, asteroid and comet collisions produce a core for Jupiter-like planets and when they gets massive enough, their gravitational pull draws in gas from the gas-rich disk of debris that circles their young star. But this model doesn't explain the formation of planets like GJ 504b that are far away from their parent star.
"This is among the hardest planets to explain in a traditional planet-formation framework," study researcher Markus Janson, a Hubble postdoctoral fellow at Princeton University in New Jersey, said in a statement. "Its discovery implies that we need to seriously consider alternative formation theories, or perhaps to reassess some of the basic assumptions in the core-accretion theory."
The discovery of GJ 504b was part of a larger survey, the Strategic Exploration of Exoplanets and Disks with Subaru or SEEDS program, which seeks to explain how planetary systems come together by looking at star systems of many sizes and ages with images at near-infrared wavelengths.
Direct imaging can help scientists measure an alien planet's luminosity, temperature, atmosphere and orbit, but it's difficult to detect faint planets next to their bright parent stars. The study's leader, Masayuki Kuzuhara of the Tokyo Institute of Technology, said the task is "like trying to take a picture of a firefly near a searchlight."
Two of the Subaru Telescope's tools in particular — the High Contrast Instrument for the Subaru Next Generation Adaptive Optics and the InfraRed Camera and Spectrograph — help scientists tease out light from these faint exoplanet sources.
The study on GJ 504b will be published in The Astrophysical Journal.