Scientists have thought that our solar system's inner rocky planets — Mercury, Venus, Earth and Mars —formed first (around 4.566 billion years ago), while gas giants and icy bodies in the outer solar ...

Dr. Rider-Stokes and his team’s findings indicate that both inner and outer solar system planets likely formed at almost the same time, around 4.564 billion years ago.

The place represents a kind of pause, a change in regime between the inner and outer solar system. Toward the sun, things are hotter, solid, smaller.

Even though the giant planets are extremely far from Mercury's orbit, their massive size more than makes up for their distance, and their motions trigger instabilities in the inner disk.

The planets, for instance, revolve in the same direction and in almost the same plane. The four inner ones (Mercury, Venus, Earth, Mars) are smaller and denser than the outer ones (Jupiter, Saturn ...

When the Sun runs out of hydrogen fuel and expands into a red giant, it will eventually encompass the innermost planets of the solar system, out to about Earth’s orbit. Being closer to our ...

The innermost planets would have formed first, so Pichierri and his team divided the TRAPPIST-1 system into two sub-groups — the inner planets b, c, d and e, and the outer planets f, g and h.

In our solar system, this is how the inner planets lost their initial atmospheres. Meanwhile, the outer planets — both farther away and more massive — held onto theirs.