Astronomy Picture of the Day

2001-01-21

Most stars appear only as points of light. In 1995, Betelgeuse became the second star, after our Sun, to have it surface resolved. Later that year, Mira was added to the list. Mira A is a red giant star undergoing dramatic pulsations, causing ...

2001-01-20

This image of the active Sun was made using ultraviolet light emitted by ionized Helium atoms in the Solar chromosphere. Helium was first discovered in the Sun in 1868, its name fittingly derived from from the Greek word Helios, meaning Sun. ...

2001-01-19

Q: Why are black holes black? A: Because they have an event horizon. The event horizon is that one-way boundary predicted by general relativity beyond which nothing, not even light, can return. X-ray astronomers using the space-based Chandra ...

2001-01-18

The first and only total lunar eclipse for the year 2001 occured on the evening of January 9/10 as the full Moon glided through Earth's shadow. Unlike a total solar eclipse, a total lunar eclipse is visible for anyone on the night side of the ...

2001-01-17

Why is NGC 3310 bursting with young stars? The brightest of these new stars are so hot that they light up this spiral galaxy not only in blue light, but in light so blue humans can't see it: ultraviolet. The Hubble Space Telescope took the ...

2001-01-16 Calvin J. Hamilton

vidence has been mounting that beneath the vast planes of ice that cover Europa lies water -- liquid oceans that might be home to alien life. The smallest of Jupiter's Galilean Moons (which include Io, Ganymede, and Callisto), Europa's deep ...

2001-01-15

Our Galaxy is filled with gas. Most of this gas is hydrogen, some is helium, but there is a trace amount of relatively heavy molecules, including carbon monoxide (CO) - a component of smog. The above wide-angle radio CO image shows the ...

2001-01-14

Johannes Kepler used simple mathematics to describe how planets move. Kepler was an assistant to the most accurate astronomical observer of the time, Tycho Brahe. Kepler was able to use Brahe's data to show that planets move in ellipses around ...

2001-01-13

Interstellar space is filled with extremely tenuous clouds of gas which are mostly Hydrogen. The neutral Hydrogen atom (HI in astronomer's shorthand) consists of 1 proton and 1 electron. The proton and electron spin like tops but can have only ...

2001-01-12

These two galaxies are interacting in a surprising way, connected by a "pipeline" of obscuring material that runs between them over 20,000 light-years of intergalactic space. Silhouetted by starlight, the dark, dusty ribbon appears to stretch ...