|
|
Browse All
:
Images of Warsaw and Goddard Space Flight Center (GSFC)
|
Printer Friendly |
Venus and Comet Pojmanski
| Title |
Venus and Comet Pojmanski |
| Explanation |
Shining brightly in the east at dawn, Venus [ http://antwrp.gsfc.nasa.gov/apod/ap060201.html ] dominates the sky in this view over a suburban landscape from Bursa, Turkey. An otherwise familiar scene for astronomer Tunc Tezel, his composite picture of the morning sky recorded on March 2nd also includes a surprise visitor to the inner solar system, Comet [ http://www.windows.ucar.edu/tour/link=/comets/ comets.html&edu=high ] Pojmanski. Cataloged as C/2006 A1 [ http://www.aerith.net/comet/catalog/2006A1/ 2006A1.html ], the comet was discovered on January 2nd by Grzegorz Pojmanski of Warsaw University Astronomical Observatory [ http://www.astrouw.edu.pl/ ] in Poland. At the time very faint [ http://www.aerith.net/pictures/comet.html#2006A1 ] and tracking through southern skies [ http://www.yp-connect.net/~mmatti/ ], the comet has now moved north and grown just bright enough to be a good target for early-rising [ http://astroblogger.blogspot.com/2006/02/ hunting-comet-pojmanski.html ] skygazers with binoculars. Enhanced and framed in this picture, the comet's tail [ http://antwrp.gsfc.nasa.gov/apod/ap000413.html ] has also grown to a length of several degrees. The comet will be at its closest approach to planet Earth, just over 100 million kilometers away, on March 5. For northern hemisphere observers in the next few days, the beginning of morning twilight really will be the best time to spot Comet Pojmanski [ http://skyandtelescope.com/observing/objects/comets/ article_1684_1.asp ]. |
|
A MACHO View of Galactic Dar
…
| Title |
A MACHO View of Galactic Dark Matter |
| Explanation |
What is our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ] made of? Stellar motions [ http://www.astro.washington.edu/strobel/milkyway.description/milkyway.description.html ] indicate there is much more mass than just stars [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] and gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ]. Photographs like the two shown above may be yielding a clue about the dark matter [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/matter.html ], however. Pictured [ http://www.astro.princeton.edu/~ogle/warsaw/event1.html ] is the first recorded instance of a dim star in our Galaxy moving in front of a bright background star, shown by the arrow, deflecting light around it, and causing the background star to appear much brighter (right frame). Were our Galaxy made predominantly of MAssive Compact Halo Objects (MACHOs), many similar such gravitational lensing events would be expected when photographing the Large Magellanic Clouds [ http://antwrp.gsfc.nasa.gov/apod/ap950918.html ] (LMC) - hence indicating the presence of MACHO lenses in our Galaxy. A research team [ http://meteor.anu.edu.au/~pjq/macho.html ] led by Charles Alcock this month claimed [ http://pio06.urel.berkeley.edu/documentation/CfPA_MACHO.html ] enough LMC gravitational lensing events to indicate at least half of the dark matter in our Galaxy is composed of MACHOs. This spectacular claim may well be correct - but awaits crucial testing with future observations and modeling. |
|
Lensing through Baade's Wind
…
| Title |
Lensing through Baade's Window |
| Explanation |
What is the shape and composition of our Milky Way Galaxy [ http://www.astro.washington.edu/strobel/milkyway.description/milkyway.description.html ]? This question would be easier to answer if there wasn't so much obscuring dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ]! In the 1940s, however, astronomer Walter Baade [ http://yorty.sonoma.edu/people/faculty/tenn/BM2B.html ] identified a "window" near the center of our Galaxy where there is comparatively little opaque dust. Now called "Baade's Window [ http://www.as.utexas.edu/PIO/SD_scripts/0816.html ]", this sky region contains millions of stars and is used for many studies of the distant Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap960623.html ]. One clever use, devised by Bohdan Paczynski, is to monitor millions of stars in our Galactic Bulge - many through Baade's window - for sudden brightening [ http://antwrp.gsfc.nasa.gov/apod/ap960202.html ] due to gravitational lensing [ http://www.stsci.edu/EPA/grav_lens.html ]. Current observations by the OGLE [ http://www.astro.princeton.edu/~ogle/warsaw/ ] and MACHO [ http://meteor.anu.edu.au/~pjq/macho.html ] collaborations have now identified dozens of gravitational amplification events. This unexpectedly large number supports previous claims that our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap960102.html ] has a "bar" of stars across the central nucleus, pointed nearly at the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ]. |
|
Stars of NGC 206
| Title |
Stars of NGC 206 |
| Explanation |
Nestled within the dusty arms of the large spiral galaxy Andromeda [ http://www.seds.org/messier/m/m031.html ] (M31), the star cluster NGC 206 is one of the largest star forming regions known in our local group of galaxies. The beautiful bright blue stars of NGC 206 [ http://www.fera.com/M31.html ] betray its youth - but close, systematic studies of variable stars [ http://redfrog.norconnect.no/~poems/poems/00535.html ] in and around NGC 206 will also accurately reveal its distance. Astronomers are searching [ http://xxx.lanl.gov/abs/astro-ph/9902382 ] for variable stars in NGC 206, particularly pulsating stars known as Cepheids [ http://antwrp.gsfc.nasa.gov/apod/ap960110.html ] and eclipsing binary star [ http://astrosun.tn.cornell.edu/courses/astro201/bin_eclipse.htm ] systems. Distances for these types of stars can be effectively determined by following the periodic changes [ http://www.pbs.org/wgbh/aso/databank/entries/dp12le.html ] in their brightness and spectra. About 3 million light-years away, an accurately known distance to NGC 206 and thus M31 [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] is critical to the larger understanding of galaxy formation, galaxy evolution, and ultimately the distance scale of the Universe [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate96.html ]. |
|
GRB 990510: Another Unusual
…
| Title |
GRB 990510: Another Unusual Gamma Ray Burst |
| Explanation |
Another huge explosion has lit up the universe, and astronomers are studying it as best they can before the light fades away. Two weeks ago, the BATSE [ http://www.batse.msfc.nasa.gov/ ] instrument on the orbiting NASA Great Observatory Compton [ http://cossc.gsfc.nasa.gov/cossc/outreach/descriptions/ ] detected unusually bright flashes of gamma-rays [ http://cossc.gsfc.nasa.gov/cossc/outreach/bro/bro2.html ] from a point deep in the southern sky. This gamma-ray burst [ http://science.nasa.gov/newhome/headlines/ast18may99_1.htm ] was also recorded [ http://www.ias.rm.cnr.it/ias-home/sax/grb990510.html ] by the orbiting Beppo-SAX satellite [ http://www.sdc.asi.it/ ], which downlinked an accurate position followed by the world's largest optical telescopes. The subsequent fading optical transient, pictured above [ http://cfa-www.harvard.edu/~kstanek/GRB/ ], is so far out in the universe its light is measured to be redshifted [ http://antwrp.gsfc.nasa.gov/apod/ap981211.html ] by factor of at least 1.6 [ http://gcn.gsfc.nasa.gov/gcn/gcn3/324.gcn3 ]. The type of powerful explosion [ http://antwrp.gsfc.nasa.gov/apod/ap990420.html ] that caused this gamma-ray burst [ http://www.sciam.com/0797issue/0797fishman.html ] is not only still unknown, but found to be fading in an unusual way [ http://www.eso.org/outreach/press-rel/pr-1999/pr-08-99.html ]. |
|
NGC 7789: Galactic Star Clus
…
| Title |
NGC 7789: Galactic Star Cluster |
| Explanation |
At 1.6 billion years old, this cluster of stars [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html ] is beginning to show its age. NGC [ http://antwrp.gsfc.nasa.gov/apod/ap990429.html ] 7789 is an open or galactic star cluster [ http://www.seds.org/messier/open.html ] about 8,000 light-years distant toward the constellation Cassiopeia [ http://www.seds.org/Maps/Stars_en/Fig/cassiopeia.html ] and lies near the plane of our Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ] galaxy. All the stars in the cluster were likely born at the same time but the brighter and more massive ones have more rapidly exhausted [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/msblues.html ] the hydrogen fuel in their cores. These have evolved from main sequence [ http://plabpc.csustan.edu/astro/stars/main.htm ] stars like the sun into the gaggle of red giant stars apparent (with a reddish-yellow cast) in this lovely composite [ http://aibn47.astro.uni-bonn.de/~gallery/articles/ imagecolor.html#tri ] color image. Comparing computer models to observations of the red giants [ http://antwrp.gsfc.nasa.gov/apod/ap990312.html ] and main sequence stars astronomers can determine [ http://adsabs.harvard.edu/cgi-bin/ nph-bib_query?bibcode=1998PASP..110.1318G&db_key=AST&high=366dca0f3d29234 ] the mass and hence the age of the cluster stars just starting to "turn off" the main sequence [ http://ast.leeds.ac.uk/research/cmd.html ] to become red giants. |
|
M3: Half A Million Stars
| Title |
M3: Half A Million Stars |
| Explanation |
This immense ball [ http://www.seds.org/messier/m/m003.html ] of half a million stars [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html ] older than the sun lies 30,000 light-years above the plane [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ] of our Galaxy. Cataloged as [ http://physun.physics.mcmaster.ca/GC//mwgc.dat ] M [ http://antwrp.gsfc.nasa.gov/apod/ap990318.html ]3 (and NGC [ http://antwrp.gsfc.nasa.gov/apod/ap990429.html ] 5272), it is one of about 250 globular star clusters [ http://www.seds.org/messier/glob.html ] which roam our galactic halo [ http://www.limber.org/globs.html ]. Individual stars are difficult to distinguished in the densely packed core [ http://antwrp.gsfc.nasa.gov/apod/ap980117.html ] but colors are apparent [ http://aibn47.astro.uni-bonn.de/~gallery/articles/imagecolor.html ] for the bright stars on the cluster's outskirts. M3's many cool "red" giant stars take on a yellowish cast in this lovely composite image while hotter giants and pulsating variable stars look light blue. |
|
|
