Echoes from the Depths of a Red Giant Star
8.04.2011

A journey to the center of a red giant star is very firmly in the realm of science fiction. But the science of asteroseismology can explore the conditions there. The technique is to time the small variations in a star's brightness measured by the planet hunting Kepler spacecraft.

Red Aurora Over Australia
1.02.2012

Why would the sky glow red? Aurora. Last week's solar storms, emanating mostly from active sunspot region 1402, showered particles on the Earth that excited oxygen atoms high in the Earth's atmosphere. As the excited element's electrons fell back to their ground state, they emitted a red glow.

Red Saturn
10.02.2005

This strange, false-color image of otherwise familiar planet Saturn shows temperature changes based on thermal infrared emission in the gas giant's atmosphere and rings. Recorded from the Keck I telescope on Mauna Kea, the sharp, ground-based picture of Saturn's southern hemisphere is a mosaic of 35 images.

APOD: 2026 January 5 Б The Red Rectangle Nebula from Hubble
5.01.2026

How was the unusual Red Rectangle nebula created? At the nebula's center is an aging binary star system that surely powers the nebula but does not, as yet, explain its colors. The unusual...

Red Crepuscular Rays from an Eclipse
30.05.2022

What's happening behind that island? Things both expected and unexpected. Expected, perhaps, the pictured rays of light -- called crepuscular rays -- originate from the Sun. Unexpected, though, the Sun was being partially eclipsed by the Moon at the time -- late last month.

The Red Square Nebula
26.09.2021

How did a round star create this square nebula? No one is quite sure. The round star, known as MWC 922 and possibly part of a multiple star system, appears at the center of the Red Square Nebula. The featured image combines infrared exposures from the Hale Telescope on Mt.

The Red Spider Planetary Nebula
29.10.2012

Oh what a tangled web a planetary nebula can weave. The Red Spider Planetary Nebula shows the complex structure that can result when a normal star ejects its outer gases and becomes a white dwarf star.

Red Nebula, Green Comet, Blue Stars
20.12.2018

This festively colored skyscape was captured in the early morning hours of December 17, following Comet Wirtanen's closest approach to planet Earth. The comet was just visible to the eye. The lovely green...

APOD: 2025 July 8 Б The Pleiades in Red and Blue
8.07.2025

If you have looked at the sky and seen a group of stars about the size of the full Moon, that's the Pleiades (M45). Perhaps the most famous star cluster in the sky, its brightest stars can be seen even from the light-polluted cities.

APOD: 2023 November 6 Б Red Aurora over Italy
6.11.2023

What was that red glow on the horizon last night? Aurora. Our unusually active Sun produced a surface explosion a few days ago that sent out a burst of electrons, protons, and more massive charged nuclei.