Signed, "A Black Hole"
16.05.1997

This artistic image is actually the signature of a supermassive black hole in the center of distant galaxy M84 - based on data recently recorded by Hubble's new Space Telescope Imaging Spectrograph (STIS). Very...

Elements in the Aftermath
31.07.2019

Massive stars spend their brief lives furiously burning nuclear fuel. Through fusion at extreme temperatures and densities surrounding the stellar core, nuclei of light elements ike Hydrogen and Helium are combined to heavier elements like Carbon, Oxygen, etc. in a progression which ends with Iron.

Radio, The Big Ear, And The Wow! Signal
17.09.1998

Since the early days of radio and television we have been freely broadcasting signals into space. For some time now, we have been listening too. Ohio State University's radio telescope, affectionately known as "The Big Ear" , was one of the first and largest listeners.

APOD: 2024 March 18 Б Comet Pons Brooks Swirling Coma
17.03.2024

A bright comet will be visible during next month's total solar eclipse. This very unusual coincidence occurs because Comet 12P/Pons-Brooks's return to the inner Solar System places it by chance only 25 degrees away from the Sun during Earth's April 8 total solar eclipse.

APOD: 2025 June 21 Б Two Worlds, Two Analemmas
20.06.2025

Sure, that figure-8 shaped curve you get when you mark the position of the Sun in Earth's sky at the same time each day over one year is called an analemma.

Venus at Night in Infrared from Akatsuki
29.01.2018

Why is Venus so different from Earth? To help find out, Japan launched the robotic Akatsuki spacecraft which entered orbit around Venus late in 2015 after an unplanned five-year adventure around the inner Solar System.

Large Sunspot Group AR 9393
11.04.2001

The largest sunspot group of the past ten years crossed the surface of the Sun late last month and early this month. The group was designated Active Region 9393 as it was the 9393rd region identified since counting officially began in 1973.

Active Region 1002 on an Unusually Quiet Sun
24.09.2008

Why has the Sun been so quiet recently? No one is sure. Our Sun has shown few active regions -- that house even fewer associated sunspots -- for over a year now, and such a period of relative calm is quite unusual.

Julius Caesar and Leap Days
28.02.2024

In 46 BC Julius Caesar reformed the calendar system. Based on advice by astronomer Sosigenes of Alexandria, the Julian calendar included one leap day every four years to account for the fact that an Earth year is slightly more than 365 days long.

Galaxies and the South Celestial Pole
31.12.2020

The South Celestial Pole is easy to spot in star trail images of the southern sky. The extension of Earth's axis of rotation to the south, it's at the center of all the southern star trail arcs.